Therma-S’well® Technology with triple-layered, vacuum-insulated construction designed to keep beverages colder or hotter, longer than all the rest. 18/8, food-grade stainless steel. Condensation-free exterior that won't sweat in your hands or bag. BPA/BPS-free and reusable. Hand-wash only. Only used once each, just changed my mind and not my color anymore, hold temps perfect! Looks slightly blue-ish and not pure white like manufacturer pics make it out to be. Selling as a set.